Safeguarding Amines from Oxidation by Enabling ...

Safeguarding Amines from Oxidation by Enabling Technologies (FE0031861) Gary T. Rochelle

Texas Carbon Management ProgramThe University of Texas at Austin

Presented at DOE Carbon Management and Oil and Gas Research Project Review Meeting

Point Source Capture ― Lab, Bench, and Pilot-Scale ResearchAugust 13, 2021

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Project Overview

• The project objective is to identify and test promising oxidation mitigation strategies for piperazine (PZ) and other solvents.

• Funding• Federal share $2,348,540• Cost share $587,058 (PI academic time + TxCMP funds)

• Overall Project Performance Dates• BP1: 3/1/2020 – 5/31/2021 (includes 3-month NCTE)

• Bench-scale• BP2: 6/1/2021 – 2/28/2022

• Bench-scale: HTOR, HGR, ASAP• SRP pilot (air/CO2/0.2 MW)

• BP3: 3/1/2022 – 2/28/2023• Bench-scale• NCCC pilot

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Three important oxidation mechanisms• 1. NO2 oxidizes all amines at 0.2 to 5 ppm in the flue gas• 2. Dissolved oxygen oxidizes amines at elevated T before the stripper• 3. Fe+3 oxidizes amines at stripper T and is regenerated from Fe+2 in

absorber

• Amine selection is an important task of the developers. It will be important as some amines are more resistant to these mechanisms than others.

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NO2: Testing to quantify the effects of NO2• Does NO2 have a catalytic effect on amine oxidation?• Will incremental oxidation be 1-2 mol/mol NO2 or 5-10 mol/mol NO2?

• More likely to see an effect in absence of other mechanisms, but it probably interacts with other mechanism.

• More likely to be catalytic at lower NO2

• Measure oxidation with and without 1-5 ppm NO2• Bench-Scale High gas flow reactor [Baseline experiment completed]

• absorber conditions missing other mechanisms• ASAP (Amine screening apparatus) [Commissioning almost complete]

• Bench-scale absorber /120oC stripper• SRP pilot plant campaign, Fall 2021• NCCC pilot plant, summer 2022

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NO2High-gas flow reactor

(HGF)

5

Pre-saturator

50 ℃

0.8% CO2 in air

90-100 cc/min

HGF50 ℃

100 cc/min0-1 ppm NO2

4 – 100 ppm NH3

Hot gas FTIR

5 L/min

5.1 L/min

180 ℃

0.3 Loaded PZ500 ml

froth

50 ppm NO2 in N2

0 - 10 cc/min

5m PZ from Alfa Aesar (0.3 loading), 50 ℃, 0.8% CO2 in air

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cumulative results

164 hours:Add 380 µmol/kg Fe3+

0

300

600

900

1,200

0 50 100 150 200 250 300 350

NH 3

accu

mul

atio

n, fo

rmat

e an

d iro

n (µ

mol

/kg)

Time (Hours)

NH3

Total Formate

Formate

Fe

2.1 µmol/kg-hr

0.9 µmol/kg-hr

1.3 µmol/kg-hr

0.7 µmol/kg-hr

153 µmol/kg step change

5m PZ from Alfa Aesar (0.3 loading), 50 ℃, 0.8% CO2 in air

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cumulative results

164 hours:Add 380 µmol/kg Fe3+

0

300

600

900

1,200

0 50 100 150 200 250 300 350

NH 3

accu

mul

atio

n, fo

rmat

e an

d iro

n (µ

mol

/kg)

Time (Hours)

NH3

Total Formate

Formate

Fe

2.1 µmol/kg-hr

0.9 µmol/kg-hr

1.3 µmol/kg-hr

0.7 µmol/kg-hr

153 µmol/kg step change

Stoichiometric relation𝐹𝐹𝐹𝐹

𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝐹𝐹=

380153

≅ 2.5

𝑁𝑁𝑁𝑁3𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝐹𝐹

=3.62.1

≅ 1.7

𝑃𝑃𝑃𝑃 − COH2 + 2𝐹𝐹𝐹𝐹3+ → 𝑃𝑃𝑃𝑃 − 𝐶𝐶𝐶𝐶𝑁𝑁 + 2𝐹𝐹𝐹𝐹2+ + 2𝑁𝑁+

Dissolved Oxygen• Vary residence time in high T rich line before stripper

• SRP pilot plant will vary time from <1 s to 40 s [modifications completed]• Measure oxygen in product CO2 at SRP (Fall 2021) and NCCC (Summer 2022)

• Remove DO from rich solvent by N2 sparging• Measure DO in cold rich solvent

• Previous testing in HTOR (High Temperature Oxidation Reactor)• SRP pilot with N2 sparging in sump (Fall 2021) [modifications completed]• NCCC pilot with sparging in sump or new column (Summer 2022

• Design of sparging column – preliminary results

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N2 Sparging in HTOR Reduces NH3 Production

9

0

0.2

0.4

0.6

0.8

1

0 20 40 60 80 100 120 140 160

NH3

(mm

ol/k

g/hr

)

Time (hrs)

N2 sparging on N2 sparging off

• Start with moderately degraded 4 m PZ solvent• Cycled from 40 to 150 °C• Liquid depth of the sparger varied between 5 to 15 cm.

N2 Sparging Model

• Mass Transfer in Liquid Phase

• Z = NTU * HTU

• No Back-mixing

• Estimation of KLa were from experiments with batch liquid by Hikita

10H. Hikita, S. Asai, K. Tanigawa, K. Segawa, M. Kitao. The volumetric liquid-phase mass transfer coefficient in bubble columns. The Chemical Engineering Journal. 22(1).1981: 61-69. https://doi.org/10.1016/0300-9467(81)85006-X.

N2 sparger design for NCCC

0

4

8

12

16

20

24

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0 0.2 0.4 0.6 0.8 1

Heig

ht (m

)

N2 Rate (mol/s)

Liquid Rate: 1.89 kg/s (15000 lb/hr), 40 C, 90% DO Removal, CO2 Capture Rate = 1.26 mol/s, D = 0.1 m so that liquid velocity is equal to bubble rise velocity

10.5 m tallN2 rate = 30 mmol/s

= 20 mmol N2/mol of CO2 captured= 16 mmol of N2 / kg of solvent

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Fe+2/Fe+3

• Measure Fe+2 and Fe+3 solubility as function of degradation [in progress]• Measure Fe+2 and Fe+3 in solvent• Adsorb dissolved Fe on activated C

• NCCC 2018-19• Niederaussem 2021• HTOR 2021-22• Bench-scale experiments 2021• SRP pilot 2021• NCCC pilot 2022

• Measure corrosion with PZ solutions: a source of soluble Fe

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Fe+2/Fe+3: Ferrous as an Oxidation Catalyst

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Ferrous as a Catalyst

• Fe increases the rate of oxidation of many amine solvents• Work on MEA focused on oxidation in the absorber• Ferrous can catalyze a free radical reaction between MEA and O2• Possible reaction pathway for PZ also• In the absence of O2, Fe still speeds up oxidation. How?

Fe+2/Fe+3 : Iron as an Oxidation Carrier to Degrade PZ in the Stripper

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• PZ oxidation occurs at high T in stripper• Ferrous should oxidize readily in the presence of DO

AbsorberDO

StripperNo DO

Ferrous

Ferric

𝐹𝐹𝐹𝐹3+ + 𝑃𝑃𝑃𝑃 → 𝑃𝑃𝑓𝑓𝑓𝑓𝑃𝑃𝑃𝑃𝑃𝑃𝑓𝑓𝑃𝑃 + 𝐹𝐹𝐹𝐹2+

Iron Becomes More Soluble as Degradation Products Accumulate

2012 CSIRO Tarong Campaign

15Nielson, 2018

Solubility of FeCl3 in 5 m PZ at 55oC

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0.02

0.04

0.08

0.16

0.32

0.64

1.28

2.56

1 2 3 4 5 6 7

Fe (m

mol

/kg)

Days

HTOR Major Degradation

Clean PZ

NCCC Moderate Degradation

NCCC Minor Degradation

HTOR Minor Degradation

Artificial Minor Degradation

Excess FeCl3 added to PZ solventsTotal dissolved Fe determined by ICP

3

3.5

4

4.5

5

5.5

6

3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000

24-h

r NH 3

in w

ater

was

h ga

s ou

tlet (

ppm

)

Operating Hours (hr)

0.106 mmol/kg/hr0.3 kg PZ/tonne CO2

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Fe+2/Fe+3: C Treating Reduces NH3with PZAS at NCCC 2019

* NO concentration relatively stable at 50 ppm

NGCCGas Rate

~8000 lb/hr

Carbon Bed

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Visual Effect of Solvents by Carbon BedCarbon Bed turned on at 5/14/2019 8:59 (3600 hrs)

Before 1 hr 1 day 2 days 9 days Fresh Solvents

Absorbance Change during the Campaign

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0

0.2

0.4

0.6

0.8

1

1.2

0

10

20

30

40

50

60

70

0 500 1000 1500 2000 2500 3000 3500 4000

540

nm A

bs (A

) (Vi

sible

)

320

nm A

bs (A

) (U

V)

Operating Hours (hr)

Carbon Bed

20

y = 0.003x + 0.095R² = 0.916

0

1

2

3

4

0 200 400 600 800 1000 1200 1400

Equi

libriu

m A

bsor

banc

e at

320

nm

(A)

Carbon loading (Δabs*g of solvent/g of carbon)

NCCC 3537

NCCC 3706

Equilibrium absorbance is linearly related to the carbon loading

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Fe removed from NCCC Used Carbon = 3.3 mmol/kg NCCC solvent

0

0.05

0.1

0.15

0.2

0.25

0.3

0 2 4 6 8 10 12

Fe (m

mol

/kg)

Batch Number

36.3 mmol Fe/kg carbon from clean carbon

At NCCC: 14 canisters of carbon 41 lb carbon/canister

12000 lbs of solvent3.3 mmol Fe/kg solvent Removed

104.5 mmol Fe/kg carbon from NCCC used carbon

High Temperature Oxidation Reactor (HTOR)

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Low TempReactor

50 °Cτ = 1.75 min

Cross Exchanger200 mL/min

7.5 L/min Sat’d air + 0.5% CO2

FTIR: NH3 and volatile aminesTotal inventory ~1.6 L

8 min per cycle

Trim Heater150 °C

τ = 1 min

Liquid samples: amine loss, degradation products accumulation (HPLC, Cation & Anion IC, ICP-OES, acid titration, UV-Vis)

Nitrogen Sparger

200 psig

Carbon Bed

23

Corrosion Method: Low-gas flow reactor

Mechanical agitationL velocity around 0.5~1 m/s

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Inlet gas 100 cc/min

25~75 °C

600 mL

C1010 corrosion & PZ concentration

25

5 m

N2

air

1

10

100

1000

0.001 0.01 0.1 1 10

Corr

osio

n ra

te (μ

m/y

r)

PZ (m)

1.5% CO2 in air/N2, 60 °C

Fresh

NCCC

Tarong

CR = 2.4 CPZ-0.68

SRP pilot campaign (Fall 2021) – test oxidation strategiesModification Purpose

Inject and measure NO2 at 2 ppm Create baseline oxidation similar tocommercial

N2 sparging in the absorber sump Test efficacy of DO stripping

Increase τ on warm rich bypass from ~1 s to ~40 s

Confirm high-T degradation in rich amine

Bypass lean amine storage tank Minimize amine inventory

Add carbon bed in rich amine line to remove iron

Test impact of removing oxidation catalysts

Adding O2 analyzers on recovered CO2 gas and rich amine

Monitor oxygen presence when perturbing system

Adding corrosion coupons Monitor corrosion simultaneous with oxidation

Conclusions on Fe+2/Fe+3

1. Fe+3 solubility in PZ varies solvent degradation from 0.02 to 2 mM2. C treating reduced ammonia production at NCCC and in HTOR. C treating removed 3 mM of “soluble” iron from NCCC solvent system. All of the “soluble” Fe must be removed to reduce oxidation.3. C treating removes PZ degradation products that adsorb at 320 & 540 nm4. >0.01 m PZ protects carbon steel from corrosion at absorber T

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This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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